罗格列酮通过与IRS—2相关的磷脂酰肌醇3激酶途径逆转慢性高游离脂肪酸引起的胰岛素分泌

目的:研究罗格列酮逆转由慢性高浓度游离脂肪酸引起的胰岛素分泌的效果并探讨介导其作用的可能信号转导机制。方法:分离纯化的SD大鼠胰岛细胞用游离脂肪酸2mmol/L或/和加用罗格列酮(0.05-10μmol/L)培养。胰岛素释放功能采用放免法测定,胰岛素受体底物-2(IRS-2)蛋白的表达水平以及IRS-2与磷脂酰肌醇3激酶(PI 3K)的p85亚单位的相关作用通过免疫沉淀和蛋白质印迹分析法检测。结果:与对照组比较,对胰岛β细胞高浓度游离脂肪酸的慢性温育显著增加了基础胰岛素分泌而显著降低了葡萄糖刺激的胰岛素分泌(P<0.01),IRS-2蛋白的表达水平降低了65％(P<0.01),IRS-2与p85的相关作用降低了73％(P<0.01)。当加入罗格列酮继续培养后,基础和葡萄糖刺激的胰岛素分泌均恢复到接近对照水平(P<0.01,P<0.05),IRS-2蛋白的表达水平增加了2.6倍(P<0.01),IRS-2与p85的相关作用增加了2.7倍(P<0.01)。PI 3K抑制物wortmannin 100 nmol/L抑制了罗格列酮逆转胰岛素分泌的作用。结论:罗格列酮逆转高浓度游离脂肪酸引起的胰岛素分泌改变,可能是通过与IRS-2相关的磷脂酰肌醇3激酶途径所介导。

Rosiglitazone reverses insulin secretion altered by chronic exposure to free fatty acid via IRS-2-associated phosphatidylinositol 3-kinase pathway

AIM: To study the effect of rosiglitazone (RSG) on insulin secretion in isolated pancreatic islets under chronic exposure to free fatty acid (FFA) and to investigate the potential signaling mechanism of RSG action. METHODS: Rat pancreatic islets were cultured with or without FFA (2 mmol/L, oleate:palmitate, 2:1) in the presence or absence of RSG (0.05-10 micromol/L). The insulin release was measured by radioimmuoassay, the expression level of insulin receptor substrate-2 (IRS-2) protein and the association of IRS-2 with p85 subunit of phosphatidylinositol 3-kinase (PI 3-kinase) were determined by immunoprecipitation and Western blot. RESULTS: The islets exposed to high FFA concentration showed an increased basal and a decreased glucose-induced insulin release as compared with control islets (P<0.01). IRS-2 protein level was decreased by 65 % (P<0.01) and the association of IRS-2 with p85 subunit of PI 3-kinase and was decreased by 73 % (P<0.01). When islets were cultured with FFA in the presence of RSG 5 micromol/L, both basal and glucose-induced insulin secretion were reversed to a pattern of control islets (P<0.01, P<0.05). The addition of RSG in the cultured medium increased significantly the expression of IRS-2 protein by 2.6 fold (P<0.01) and the association of IRS-2 with p85 by 2.7-fold (P<0.01) as compared with islets incubated with FFA alone. The effects of RSG on insulin secretion were blocked by a PI 3-kinase inhibitor, wortmannin. CONCLUSION: The effects of RSG on insulin secretion could be mediated through an IRS-2-associated PI 3-kinase signaling pathway.